Before handling the message, the function process() needs to check that the message was previously included in some Merkle tree state root which would be acceptable.
Acceptable state roots are those that were previously proven, or have been stamped as confirmed.
在处理消息之前，函数 process() 需要检查消息之前是否包含在某个可接受的 Merkle 树状态根中。
可接受的状态根源是那些先前已被证明或已被标记为已确认的状态。